A dental floss holder is generally comprised of a holding portion, and a head portion used for tensioning a dental floss, the dental floss holders may be broadly divided into two types according to the relationship between the tensioned dental floss and the holding portion. As for the first type, the length direction of the holding portion of dental floss holders is generally parallel to the extension direction of tensioned dental flosses. The dental floss holders are relatively common and applicable for cleaning the teeth in the middle of the gums. But as for the teeth adjacent to both ends of the gums, such as wisdom teeth, due to the space limitation of the oral cavity, when the head portion of the dental floss holder is into the positions, the direction of the dental flosses may be deviated from the direction of interstices between teeth, and thus the cleaning work is relatively difficult. As for the second type, the length direction of the holding portion of a dental floss holder is perpendicular to the extension direction of its tensioned dental floss. This type of dental floss holders are applicable for cleaning the teeth adjacent to both ends of the gums but may be operationally inconvenient when used for cleaning the teeth adjacent to the middle of the gums. Because of the defects in design, both the two types of dental floss holders are not ergonomically designed, and are not conducive to fully and effectively clean the teeth.